This assembly is from 1957 from a Raytheon manual, but can be modernized using a BC548, 6 V power supply and common 100 mA relays.
In the figure we show how to activate a relay from the output of a common operational amplifier when...
Found in a publication from the 50's, this circuit uses a germanium transistor of the time. The...
November 2016 - Mouser Electronics already has the Arduino Shield 101 for IoT applications with...